The invention is based on a reciprocating piston pump element of a reciprocating piston pump as defined hereinafter. Such reciprocating piston pump elements are known in the prior art (DE 32 36 536 A1, German Patent Application P 43 20 902.5) and have integrally embodied cylinders and cylinder heads that are embodied as integral components. The outlet valve seats are machined into the cylinder heads. The cylinder heads are adjoined axially by necks, which in turn are adjoined by circularly bounded flanges. The outlet valve housings have tubular extensions that are slipped over the flanges and crimped onto the necks. The tubular extensions are thin-walled and are an aid so that before the cylinders are inserted into the housing blocks, the cylinders and the various outlet valves can be combined into structural units; the advantage is that before this insertion, the closing springs can already be prestressed, so that the valve seat closing elements are protected against being lost. Another advantage is that the outlet valves can be checked for functionality and tightness before being inserted into the housing blocks. In the region of the ends oriented toward the atmosphere, sealing rings are associated with the outlet valve housings, so that these housings additionally have the function of closing elements for the bores of the housing blocks. Once these reciprocating piston pump elements have been inserted into the bores of the housing blocks, the outlet valve housings are pressed against the cylinder heads by means of headless screws. Accordingly, in a pumping operation, such a headless screw is loaded by a force that is at least as strong as the highest pressure generatable by the reciprocating piston pump element, times the cross-sectional area of the bore. In the present example, the reciprocating piston pump element is driven so forcefully that it generates a pressure of up to approximately 300 bar.
Reciprocating piston pump elements of this kind are used for instance in pairs, facing one another, inside housing blocks of anti-lock systems for vehicle brake systems, as in International Patent Reference WO 93/08050. Such housing blocks, because they should be as light in weight as possible, are usually of lightweight metal and accordingly require relatively long threads for the headless screws. Nevertheless, for safety reasons, the threads must be made especially carefully and therefore expensively. As can be seen from FIG. 5 of WO 93/08050, such headless screws claim a disproportionate share of the dimensions of the associated housing block.